what wire size for what amperage?

on mtnelectronics they sell different wire sizes, and coatings.
If I were to drive a c8 with xml2 at 4.5 amps what size is sufficient? and what coating is best?
what can a 22 awg handle?
or 18?

22awg is more than enough for a single LED even at direct drive. For a triple you should consider 20awg but I have used 22 just fine (if the cable if short enough).

Silicone coating is softer and easier to solder, I have never used the other one.

I think 18awg is overkill for any flashlight unless it’s a monster build, multi XHP70 and such.

Common US wire gauges - AWG gauges and their current ratings

According to that 18ga would be about right for 4.5 amps, but I think DC ratings are a little different. A solid single strand wire should carry more amps than multiple strand wire does. We use multiple strand wire because it's more flexible and much easier to use in flashlights.

Great. Thanks guys. Can I use solder with flux inside or do I need additional flux?

I always use extra flux. It’s cheap and makes it much easier.

Ok, what flux should I get? Is there any that are suitable at Home Depot or Walmart, or should I order a particular one?

To me, pluming solder sucks for electronics. I use 60/40 rosin core solder from Radio Shack and Rosin flux from Radio shack, but you can get better, like kester solder, on ebay. I use 60/40 because it works for me, but it does have lead in it. I never could get the lead free stuff to work for me.

I use Bernzomatic 60/40 rosin core from Home Depot for bigger jobs, and some nicer 63/37 MG chemicals stuff in a thinner diameter for the finer jobs. I keep Kester liquid flux on hand as well, but it isn’t really necessary for soldering emitter wires and stuff. I use it when soldering to pills and big things that suck up the heat.

And for the record on wire diameter, I agree with what will34 said earlier

Thanks guys. I have a cart of things from mtn and from Simon. I am going for it!